Wisconsin’s utility customer advocacy group has joined landowners, local governments and environmental groups urging Wisconsin regulators to reject a proposed high-voltage power line project, which they call outdated technology.

In a legal brief filed Friday, the Citizens Utility Board said there’s no evidence the $500 million line, known as Cardinal-Hickory Creek, is needed for reliability and it may not deliver the benefits its owners promise.

The group, which represents the interests of residential and small business ratepayers, said the project appears to provide more benefits to out-of-state power producers than ratepayers and that there is a “significant risk that the line, if constructed, will result in net costs rather than net benefits for Wisconsin customers.”

The utilities and clean energy advocates say the line is needed to bring power from the west to population centers, and that numerous existing and planned wind and solar projects are depending on it to deliver their full output.

They argue the line will deliver between $23 million and $350 million in net benefits to Wisconsin under “the most plausible” future scenarios studied. In the worst-case scenario, they say, it would cost Wisconsin customers just $25 million over 40 years to relieve congestion that is keeping wholesale energy prices higher than in neighboring states.

The Public Service Commission must decide by Sept. 30 whether the project is needed and in the public interest.

Opponents argue the line is an old approach to generate profits for its owners. They say there has been inadequate study of newer and cheaper alternatives, such as in-state solar and battery storage.

“This Commission has to save the utilities from their penchant for living in the past,” wrote SOUL, one of more than a dozen groups fighting the project.